M. Leuckart on the genus Sacculina. 427 



intestine, which is destitute of a muscular coat, possesses little 

 to characterize it, this negative result must not be estimated at 

 too high a value, especially considering the other circumstances 

 that occur here. 



The external integuments consist of a thick and rcsistent 

 yellowish chitine-laver, which has not the least resemblance to 

 the integuments of the worms, but in its appearance and physi- 

 cal behaviour closely approaches the chitinous shield of the 

 Arthropoda. From its appearance under the microscope, one 

 might almost suppose that it is composed of numerous mem- 

 branes stuck together and much folded, — a supposition which 

 acquires still more probability from the fact that similar thin 

 and folded chitine-lamcllse arc also to be met with in abun- 

 dance in the interior of our animal, especially in llathke's 

 ovaries. 



Segmentation, as is well known, is wanting in the Sacculina; 

 the chitinous skin is throughout of the same thickness and 

 nature. Beneath the chitine coat there lies, besides the ordinary 

 epidermoidal cellular layer, a tolerably thick whitish layer, which 

 separates readily from the outer integuments, and appears to be 

 a sort of fatty body, or a cutaneous muscular sac permeated by 

 fat. In it, besides numerous cellular bodies and granules, we 

 find the above-mentioned chitinous lamella?, and single broad 

 muscular fibres with most beautiful transverse striation. In the 

 part surrounding the posterior orifice, these muscular fibres 

 attain their greatest development ; they become developed here 

 into a regular sphincter, which is so powerful, that, in the con- 

 tracted state, it forms a distinct wart-like elevation (fig. 5). 

 During life, the body of the animal is very frequently seen in 

 slow undulating movement, which is evidently the result of the 

 cooperation of the cutaneous muscles. 



The posterior orifice (which in Peltogaster with a ventral 

 mouth is turned forwards, that is, towards the head of the host 

 and the orifice of the shell) is certainly not the mouth, as llathke 

 supposed, but rather a cloacal aperture. It does not lead into 

 the alimentary organ, but into the brood-chamber of our Saccu- 

 lina. This cavity occupies by far the greater part of the whole 

 body, and has its own chitinous walls, which pass over, at the 

 margin of the orifice, into the external integument, and, during 

 the contraction of the sphincter, form a number of radiating 

 folds at this point. The thickness of this chitinous wall is cer- 

 tainly much less than that of the external integuments, but still 

 very considerable. 



The contents of this brood-chamber consist of a great quantity 

 of flat bands, of about 1 line in breadth on an average; these 

 issue from each other in an irregular dichotomous ramification 



